Transcranial Direct Current Stimulation (tDCS) Induces Analgesia in Rats with Neuropathic Pain and Alcohol Abstinence

Neuromodulatory techniques have been studied to treat drug addiction or compulsive eating as well as different chronic pain conditions, such as neuropathic and inflammatory pain in the clinical and preclinical settings. In this study, we aimed to investigate the effect of transcranial direct current stimulation (tDCS) on the association of alcohol withdrawal with neuropathic pain based on nociceptive and neurochemical parameters in rats. Thirty-six adult male Wistar rats were randomized into five groups: control, neuropathic pain, neuropathic pain + tDCS, neuropathic pain + alcohol, and neuropathic pain + alcohol + tDCS. The neuropathic pain model was induced by chronic constriction injury (CCI) to the sciatic nerve. Rats were then exposed to alcohol (20%) by oral gavage administration for 15 days (beginning 24 h after CCI). tDCS was started on the 17th day after surgery and lasted for 8 consecutive days. The nociceptive test (hot plate) was performed at baseline, 16 days after CCI, and immediately and 24 h after the last session of tDCS. Rats were killed by decapitation, and structures were removed and frozen for biochemical analysis (nerve growth factor and interleukin (IL-1α, IL-1β, and IL-10 measurements). Neuropathy-induced thermal hyperalgesia was reversed by tDCS, an effect that was delayed by alcohol abstinence. In addition, tDCS treatment induced modulation of central levels of IL-1α, IL-1ß, and IL-10 and neurotrophic growth factor. We cannot rule out that the antinociceptive effect of tDCS could be related to increased central levels of IL-1α and IL-10. Therefore, tDCS may be a promising non-pharmacological therapeutic approach for chronic pain treatment.